Tech Tuesday - Shimano Brake Bleed

If you've never had a go at bleeding your Shimano brakes, now is the time. Today's Tech Tuesday is here to guide you through the steps from start to finish and there is no reason to be intimidated - it's easier than you think! Inside you'll find some helpful pointers and a great video showing you the process.

Get your tools and mineral oil and learn something new today!

How do you know when to bleed your brakes? As a very general rule, one should replace the fluid in their brakes at least once per year, even if you don't notice any degradation in performance. If you ride more than average, or spend a lot of your saddle time in a bike park banging out laps on the char lift, you may want to do a bleed more often. A quick check of the fluid by leveling the lever so it's parallel to the ground and removing the reservoir cap will allow you to see if the mineral oil in the system is cloudy or dark with contamination. Keep in mind that some mineral oil is darker than others, but if it looks hazy or you spot any floating bits, it is time to perform a bleed. Likewise, a spongy feel at the lever, excessive lever pull, or brakes that pump up (meaning the bite point changes when they get hot during use) all mean that it is time to do this job.

Some pointers before you begin...

• As always, a clean work area can make this job go smoother. Take a minute to clean up your bench and put away the tools that you won't be using.• Always remove your pads and put them somewhere that they won't get fluid on them when you make a mistake and get drenched. It will happen at some point. Likewise, put your wheels in a safe spot as well... Not leaning up on the repair stand under your bike!• Remember that you may have to overfill your Shimano system while bleeding which could make a bit of a mess. While mineral oil isn't going to cause damage like DOT fluid can, you may still want to put an old towel on the floor, under your bike. • While some Shimano brakes incorporate a small phillips screw that you can use to adjust the bite point of the brake, its range is very limited and has little effect. If you're looking for less lever pull than what the screw allows, now is the time to make that adjustment. With the bleed nipple on the caliper closed, gently pull the lever to pump the pistons out ever so slightly. Remember that having the pistons protrude only an extra millimeter can have a huge effect on the lever pull. You can test the results by reinstalling your pads, after being sure to clean any mineral oil that may have been present on the caliper, and giving the lever a squeeze once you've place a rotor between them. If you've gone too far you may get some pad rub on the rotor. Reset the pistons using a plastic tire lever and try again.

When bleeding your Shimano brakes you'll be working the fluid from the reservoir at the lever down the line and out of the bleed nipple at the caliper. It is important to not let air be introduced to the system by letting the oil level in the reservoir get too low during this process. To prevent this, drip the new mineral oil in from the bottle as you prime the system. Old oil will be expelled from the caliper and drain into the bottle. Once you can visually see the new oil is being pushed out of the caliper you will know that a full bleed has been performed. Finish it up with the last few steps to fully rid the brake of any air that may be trapped.

What fluid should you use in your Shimano brakes? Most importantly, never use anything other than mineral oil in your Shimano stoppers, and I highly recommend using Shimano branded oil. Many other brake systems use DOT brake fluid, the same as your car uses, but the two fluids have very different properties and are not interchangeable. The rubber seals in your Shimano brakes will be quickly eaten away by the much more corrosive DOT fluid, rendering your brakes useless in no time. A quick stroll through your local pharmacy or auto store will show you that there are a number of different mineral oils available, but the majority of those will not work for this job. Many of those oils will be far too thick to work well, or have perfumes and other chemicals that will damage your brake system. Anything mineral oil from a pharmacy will not only be too thick, but is intended to be used as a laxative. Use that stuff when you need to pooh, not stop your bike. Likewise, a quick search of the forums and you'll see people exclaiming how they've used fork oil or automatic transmission fluid... there is a good chance that both of those options are too thick and will make your brakes feel sluggish, not to mention possibly having additional chemicals in them that could damage the seals in your brakes. What should you use? Despite it costing quite a bit more than some alternatives that may or may not work, I always recommend using Shimano branded mineral oil. I'm sure many readers will pipe up with options that they've used in the comment section below, but by using Shimano mineral oil you'll know that you won't have any problems. Yeah, it costs quite a bit, suck it up and buy the right stuff though and you'll know that you won't have any issues.

To do this job you'll need a set of hex wrenches, a small phillips screwdriver, a 7 mm wrench, a clean rag, some isopropyl alcohol, the yellow Shimano bleed block, some tubing and a bottle or small plastic bag, and of course some Shimano mineral oil.

I've seen people bleed their Shimano brakes a few different ways with successful results, but the routine above is how I prefer to get the job done. Do you do something different? Have a trick or tip that you'd like to share? Put it down below!

Great tech tuesday! I have noticed that it's alot of people that don't know how to bleed their Shimano brakes. This video proves that it probably is the easiest brakes to bleed once you know the basics. I agree with that the way you bleed them is the easiest, even though I use the (unnecessary) Shimano bleed kit.

Its a good tutorial, though one thing I would like to add that was not mentioned. Always clean the caliper pistons before you re-seat them with the bleed block, Otherwise your likely pushing dirt and brake dust into your seals. This is especially critical with shimano, as replacement parts for these brakes are hard to come by and not always available from part vendors.

Bleed from caliper and siphon from reservoir works the best. Best with 2 people. Rock solid results. Shimano recommended bleed is a shade tree tailgate strategy. Not ideal. Bleed block not needed right way. First bleed up then close bleed. Tape towel around reservoir. Install pads and rotor. Squeeze lever to work out and air. Top off and be stoked.

I definitely prefer "overflow" bleeding from the caliper to the lever versus the method described in this installment. Also a great trick to help make your brakes feel rock-solid is to [after bleeding] immediately cinch the lever down to the bar tight, with a rubber band or pedal strap or something similar, and leave it for a few hours (overnight if possible). This will allow any left over air bubbles time to rise to the reservoir because it holds the system open. I have made some of the best-feeling hydraulic brakes with this method.

So after leaving it for a few hours, you release the rubber band and any air bubbles sitting against the piston in the lever pop right out into the reservoir, right? That sounds like a good idea if you are not in a hurry. This should work with any brake system which has a reservoir which can vent to the atmosphere.

My rear saint still feels like crap after I did all of this multiple times! Why??? I have no modualtion. Also the rear leavers barrel adjuster and free stroke are all the way out, as far as they can go and is still feels like shit. The fronts not even fully adjusted and it feels firm and nice. Could u be that the leaver is f**ked? And I would need a new one?

There was nothing about caliper positioning, like having the nipple be the highest point in the caliper, disregaurding this fact may result in a bit of air getting trapped. Other than that, good video. I prefer to bleed it more like a car where I squeeze the lever, then close caliper then pump it back up, refill and repeat. Same idea though

air does what? It rises bubbles rise so why would you bleed top to bottom and try and get air out of the system. Now if he held the caliper up in the air the result could be better, but this method which requires gravity wouldn't work.

Gravity makes the fluid flow downwards along with the bubbles, when you open the reservoir... then you can close the bleed screw at the bottom and leave the reservoir open for night to make sure everything went up...

holder for the bottle is DIY, just grab anything wires or whatever and make it hang on something.
and the tools he's using is not actual shimano bleed kit aside from the mineral oil bottle. but doing it his way is more pain in the ass but it's a lot cheaper compared to buying proper bleed kit from shimano.

I've done both, but with proper top-down technique you can get the air out. I prefer top down because it's cleaner and I do not have to take pads or wheel out. So bleeds are way quick and a get a solid lever still. But I do it a tad differently than the video- I close the caliper with the lever compressed so the vacuum at the master cyclinder pulls air up through the sytem

The best and easiest way is to use 20ml and 50ml plastic syringe (you get the pharmacist), which is suitable for 4millimeters thick (inside) the hose and fill 50ml syringe Shimano mineral oil and put the oil brake caliper bleed valve and suck at the same time, 20ml syringe brake fluid reservoir excess oil (first remove the brake pads and put the "yellow piece of 'in their place), when you have put about half of the oil (in the 50ml syringe), then close the valve and press the brake lever and tap the brake hose that you get all the air out, if you can not then do the same again and make sure that all the air comes out, then just a tank full oil, close the cover and drive! Hopefully, I could write this even though I am understandably Finnish ... : D

I find that the Juicy bleed kit (in general, a syringe) provides the best bleeding solution. I bleed Shimano's the other way, and have a bucket hanging off the bar to catch the excess fluid. Yes, it is more messy, but it also seems to work well. I've also modified a Juicy syringe to bleed Hayes brakes as well and it works awesome. However, I'm up for trying anything so I'm going to give this way a go, cause it's for sure the cleanest brake bleed I've ever seen!!!!

Just a comment. I use Castrol HYDRAULIC SYSTEM MINERAL OIL. They use it in some old Jaguar cars for their complicated hydraulic systems. (www.motorcarsltd.com/JLM9886.html) . I've bleed my shimano saint brakes in year 2008 with this oil & since then i only change pads. Never done any bleeding. So i have handful proof that it works, and it is very cheap (costs less than 10$ for a 500ml bottle). Shimano mineral oil is a rip-off.

I've used Johnson & Johnson Baby oil before. It is pretty much pure mineral oil, with slight additives for the smell. Yeah someone is gonna say "but the chemicals from the aromatics are going to eat your seals". I haven't had it happen yet and I seriously doubt it. My brakes work great with it in them. I even tested out the feel by putting real shimano fluid in one brake and baby oil in the other. Guess what? They felt EXACTLY the same. If you are in a pinch, or can't afford the shimano stuff. Baby oil works great.

Super old comment, but couldn't help but to say...I hope you are joking.

Baby Oil is not Hydraulic Mineral Oil. It's just Mineral Oil. The Additives will not "eat" your seals but just slow up your system.

Pentosin 7.1 or CHF PLUS is better than Shimano (rebranded generic) with a lower viscosity and used in German auto's hydraulic power systems. With Pentosin, one should actually see/feel an increase of performance!

Can't say cause i've never tried the baby oil stuff lol, but technically it should slow it up, but then again if your friend really hasn't had any problems as far as slower performance then there isn't anything to argue about.

mineral oil doesn't absorb water and the seals DO protect the oil from pollution for a long time. I've bled my friend's 3 yrs old shimano deores and the oil was totally clean. It's also about the braking style, daily fried oil may not be the best Of course, if the brake performance differs during the riding or it doesn't have the right power, it's time to bleed. Preventive bleeding after a season is a waste of time (but it doesn't take THAT much time, i know) ;-)

or the creaking comes from somewhere else in the bike. believe it or not, i work in a bikeshop and a person thought it was his fork that creaked when it compressed when he pedaled hard uphill. it was the rear hub. -.-

Interestingly I thought so for my previous frame (KHS XC Team) but found it was the linkages. Specifically the chainstay link bolt. I had overtightened it and actually fractured the bolt head. I didn't see this until I took it apart again because I was selling it and needed to clean it up. I had replaced the BB and ensured it was greased. I didn't think about the rear hub but I don't think that was the issue because I'm using the same wheelset on my new frame. Frame creek is one of those things that are really a trial and error thing IMO. In any case I'm sure we can leave the troubleshooting aspect to the pros here.

Oh man, that would be a tricky Tech Tues to do - there can be so many things! Creaks can be especially hard to track down sometimes, especially on aluminum bikes. As always, test ride the bike and try to narrow down the source first. Does it do it when you stand up? If so, it isn't your post/seat/post clamp. Toss in a different rear wheel to eliminate that source as well. I'd say that over 80% of the time it ends up coming from the BB/crank/pedal area. But I've seen lots of noise come from the front derailleur clamp, bottle cage, stem/bar clamp, and lots of other places.

As mentioned in the video/article, the same process can be applied to other Shimano brakes as well. If in doubt, check the Shimano website tech docs (link in the article) to see the instructions for your brakes.